Sick Birds, a continuing problem.

OK I have posted a few times with out a resolution, and I will try to be complete in my story.

So far I have gotten 3 batches of chickens.

April, June, and November.

After about 6-7 weeks, the new birds which seem otherwise healthy start dieing.

There is nothing different about their poop, diet, water, or dwelling. The new birds have been isolated for a month, and seem fine until after they go into the coop.

The coop was built in April.

The Birds go from healthy to seeming week on day one (Still eating). They loose weight and die normally within a few day(2-4). I have wormed, Corrid, and deloused.

The new birds other then sharing the same air, are separated once moved into the main coop.

Of the first group of 30 I lost 4.
Second group of 12, I lost 6.
Third group of 4 lost one, and one is on her way out. These last two have been getting the works from an animal rehabbed as I am at a loss, and it seems she is stunned as well.

Are they vaccinated when you get the chicks? It could be possible that your flock is a carrier and once exposed to them they become ill. I would have a neucropsy(or however you spell it) done on the next one that dies to see if they have been exposed to something.